Current climate impact assessment
methodologies for water resources
rely on indicators like rainfall
distribution, water level monitoring
on surface water storage structures
and streamflow behavior. This gives
little lead-time to formulate
strategies for intervention before
the occurrence of extreme weather
events like floods and drought. The
ENSO forecasts currently available
provide enough lead-time to
pre-assess potential impacts. In
this session, the participants
shared methodologies and procedures
to carry out potential impact
assessments relating to the water
resources sector by using climate
forecast information.
Presentation Highlights
Joesron Loebis reported that the ECE
pilot project provided an
opportunity to collect data on
streamflow and flood-drought
incidences to assess the impact of
ECEs on streamflow through a
correlation coefficient method. Due
to large data gaps, it was not
possible to assess the impact of
factors like watershed degradation
and deforestation on streamflow. A
case study of Lake Toba established
that river flow variations are
highly correlated with ENSO-related
rainfall behavior. Constraints
included data availability, pointing
to the need for a better data
network so that predictions are
convincing. He also pointed out that
flood forecasting needs to become a
political will of the government.
For
the Philippines, Susan Espinueva
discussed how the National Water
Resources Board and the National
Power Corporation assess potential
impacts through reservoir operation
simulations after the receipt of
forecasts from PAGASA. These
simulations determine the projected
available water in the reservoirs
and serve as a basis for water
releases or allocation to various
users.
The
results of a study using inflow data
from five major Luzon reservoirs and
a Mindinao lake were presented. This
ECE research study enabled the water
resource sector to document past
data and relate it to ENSO indices
through correlation techniques. The
results of the study indicate the
potential opportunities to utilize
ENSO forecast information for water
resource management in the
Philippines.
The
major conclusion was that
significant associations between
climate variability (in terms of
rainfall) and hydrologic activity
(in terms of reservoir inflow) exist
at varying magnitudes in the study
area. Therefore, improved knowledge
on the relationship of these
variables would be an initial step
in better planning and management of
water resources systems, whether
they are designed and operated for
the purposes of water supply,
irrigation, flood control or
hydroelectric power generation.
Lessons learned and recommendations
include:
-
Documentation is a
time-consuming process. With
limited time to conduct the
study, and with so many agencies
involved in water-related
activities, only
readily-available data were
collected and analyzed only with
simple statistics.
-
Responses of water-related
agencies were delayed, even with
an announcement by PAGASA of an
imminent La Nnœa or El Niœo.
-
Further study should concern:
in-depth assessment of the lag
correlation between rainfall and
streamflow, and the ENSO
indicators for potential
forecasting of these
hydroclimatic variables;
modeling the rainfall-runoff
phenomenon to identify or
differentiate the factors
(climatic or man-made) affecting
changes in watersheds; and
identifying methodologies to
assess potential impacts of ECEs.
-
The documentation and analysis
of ECEs should be
institutionalized to ensure the
use or adoption of the
methodologies.
Tran
Thanh Xuan reported on the outcomes
of a study using correlation
coefficient methodologies between
ENSO events and river runoff. It was
carried out in Vietnam by selecting
15 large and small rivers in various
agro-climatic zones. Small and
medium-sized rivers in Central
Vietnam showed more significant
sensitivity to ENSO than the larger
rivers in different regions.
Long-term time-series data provide
better resolutions of linkages than
the short duration time-series data.
The study used a rough method for
analyzing the effect of ENSO on
water resources, which suggests that
a proper time-series analysis of
Southern Oscillation Index (SOI) and
runoff could result in a reliable
river flow prediction. More detailed
time-series models could be
developed that would relate monthly
runoff to SOI values at different
lag times.
Discussion Points
The
presentations highlighted the
impacts experienced at the extreme
ends of the hydrological continuum,
from droughts to floods. At these
extremes, there are secondary
impacts that have been experienced.
During droughts, there are
frequently wildfires, which further
tap the limited water resources. At
the opposite end, the flooding
results in loss of homes and lives.
Indirectly, these extremes have an
impact on the ecology and the
economy of local and national
governments. Therefore, it is
important to engage in integrated
water resources planning.
The
contribution of environmental
degradation over a period of time
affects climate variability and
water resource variations. This
factor needs to be accounted for
while drawing conclusions. There is
a need to fix unit-wise threshold
levels. The interventions on account
of climate variability-associated
fluctuations could be done only when
it is anticipated that the water
supply level could be below
threshold levels.
Recommendations
The
discussions revealed that there are
a number of policy and planning
actions that can be taken to reduce
the impacts of floods and droughts.
Participants recommended the
following:
-
Develop a better data network so
that agencies can be convinced
of the quality of their
predictions.
-
Flood forecasting needs to
become a political will of the
government.
-
Prioritize critical river basins
for undertaking studies to
establish linkages between water
resource flow and climate
variability.
-
Conduct further study in terms
of:
-
in-depth assessment of the lag
correlation between rainfall and
streamflow and the indicators of
ENSO for potential forecasting
of these hydroclimatic
variables.
-
modeling the rainfall-runoff
phenomenon to identify or
differentiate the factors
(climatic or man-made) that
affect changes in watersheds and
catchments.
-
identify methodologies to assess
potential impacts of ECEs.
-
Bring meteorological and
hydrological people together. In
both sectors, priorities need to
be identified where these
interactions are important.
-
Strengthen hydrological research
institutions in each country, by
incorporating ENSO contents into
research agenda.
-
Convince the government that
data collection is important for
analyzing risks and
vulnerability to extreme events,
and for developing mitigation
strategies.
-
Maximize partnerships for data
collection, involving agencies,
the private sector, communities,
districts and provinces
